Maternal depression (MD) negatively affects the mother and child's health and development with prevalence rates ranging from 10-50% in the perinatal period, but is generally undetected and untreated in obstetric care. A randomized by clinic design will be used to test the effectiveness of an innovative collaborative model, Partnership for Women's Health (PWH), designed to screen prenatal and postpartum women for MD. PWH is aimed to increase the ability of health care providers to follow clinical guidelines, offer evidence-based practices, and productively interact with patients through a collaborative partnership with existing community programs. PWH links patients to services as a result of appropriate and timely identification of MD. PWH includes a Mental Health Advisor to support providers and proactively contact depressed women linking them to appropriate treatment. In addition, the proposed study will elucidate the critical components of effective collaborative models for screening/referral partnerships within and across systems of care, and pursues aims that reflect balanced interest in empirically and clinically derived knowledge. Specific Aims: (1) To evaluate the effectiveness of the PWH model compared to usual services (CONTROL) to identify MD, increase service referrals and service receipt to appropriate mental health services, within primary obstetric settings serving ethnically diverse, low income pregnant women in CPSP populations;(2). To determine the impact of PWH service referrals and service receipt on maternal and child outcomes;(3) To examine whether intimate partner violence and alcohol, tobacco, other drugs moderate the effects of the PWH model on service referrals, service receipt, and maternal and child outcomes;(4) To examine intervention implementation and fidelity across clinics receiving the PWH model and (5) To conduct a cost effectiveness analysis of the PWH model. We propose to adopt a mixed-method design combining the quantitative assessment of treatment outcome with a qualitative assessment of treatment process examining sociocultural and organizational context related to program sustainability. A total of 16 clinics will participate, each serving Medi-Cal CPSP mothers throughout San Diego County. All women receiving prenatal services at each of the clinics will be screened for MD (n = 6000), and a sample of 600 women who screen positive will be enrolled in the study and prospectively followed up to 12 months post delivery. Findings have the potential to improve pregnancy outcomes among culturally diverse depressed mothers by intervening early, which will enhance the women's health and ability to care for their newborns.